US8041144B2ActiveUtilityPatentIndex 84
Apparatus and method for improving visibility of an image in a high illuminance environment
Est. expiryOct 17, 2026(~0.3 yrs left)· nominal 20-yr term from priority
H04N 1/407H04N 1/6088H04N 5/57
84
PatentIndex Score
7
Cited by
20
References
16
Claims
Abstract
An apparatus and method for improving visibility of an image. The apparatus includes: a lookup table (LUT) generating module generating an LUT having image data in a high illuminance environment corresponding to image data of an input image set therein so as to increase lightness and chroma of the input image according to external illuminance; an image mapping module mapping the image data of the input image into the image data in the high illuminance environment on the basis of the generated LUT; and a local contrast increasing module increasing local contrast of the mapped image data using a parameter for adjusting the local contrast according to the external illuminance.
Claims
exact text as granted — not AI-modified1. An apparatus for improving visibility of an image, the apparatus comprising:
a LUT (lookup table) generating module to generate, using one or more processors, a LUT having image data in a high illuminance environment corresponding to image data of an input image set therein so as to increase lightness and chroma of the input image according to external illuminance;
an image mapping module to map the image data of the input image into the image data in the high illuminance environment according to the generated LUT; and
a local contrast increasing module to increase a local contrast of the mapped image data using a parameter for adjusting the local contrast according to the external illuminance,
wherein the local contrast increasing module comprises:
a lightness computing module to compute the lightness of the input image and a lightness of the image into which the input image has been mapped by the image mapping module;
a low pass filter to filter luminance data of each of pixels constituting the input image and luminance data of each of pixels constituting the image into which the input image has been mapped;
an index computing module to compute a contrast ratio index and a contrast index with respect to the input image according to the filtered luminance data and average luminance data with respect to all of the pixels constituting the input image; and
a local contrast compensating module to increase a local contrast of a pixel region corresponding to the parameter according to the contrast index and the contrast ratio index.
2. The apparatus of claim 1 , wherein the parameter is data corresponding to a duration of sensed illuminance.
3. The apparatus of claim 1 , wherein, when image data corresponding to RGB image data of an arbitrary pixel of the input image is not set in the generated LUT, the image mapping module interpolates adjacent image data and maps the interpolated image data.
4. The apparatus of claim 1 , wherein:
the contrast index is determined by an equation:
contrast_index
=
Y_mean
-
Y_pixel
Y_mean
+
Y_pixel
,
where Y_mean represents an average value of luminances of all of the pixels constituting the input image and Y′_pixel represents a luminance of each of the pixels constituting the image into which the input image has been mapped.
5. The apparatus of claim 1 , wherein:
the contrast ratio index is determined by an equation:
contrast_ratio
_index
=
Y_pixel
_fitered
Y_pixel
or
,
contrast_ratio
_index
=
Y
′
_pixel
_filtered
Y
′
_pixel
,
where Y_pixel represents a luminance of each of the pixels constituting the input image, Y_mean represents an average value of luminances of all of the pixels constituting the input image, Y_pixel_filtered represents a filtered Y_pixel, Y′_pixel represents a luminance of each of the pixels constituting the image into which the input image has been mapped, and Y′_pixel_filtered represents a filtered Y′_pixel.
6. The apparatus of claim 1 , wherein the local contrast compensating module determines whether the corresponding pixel region is a dark region or a light region according to the contrast index.
7. The apparatus of claim 6 , wherein, when determined that the corresponding pixel region is the dark region, the local contrast compensating module decreases a luminance of the corresponding pixel region using the parameter.
8. The apparatus of claim 6 , wherein:
when determined that the corresponding pixel region is the light region, the local contrast compensating module determines whether to increase the local contrast of the corresponding pixel region according to the contrast ratio index, and
when it is determined that the local contrast of the corresponding region needs to be increased, the local contrast compensating module increases a luminance of the corresponding region using the parameter.
9. A method of improving visibility of an image, the method comprising:
generating a LUT (lookup table) having image data in a high illuminance environment corresponding to image data of an input image set therein so as to increase lightness and chroma of the input image according to external illuminance;
mapping the image data of the input image into the image data in the high illuminance environment according to the generated LUT; and
increasing a local contrast of the mapped image data using a parameter for adjusting the local contrast according to the external illuminance,
wherein the increasing of the local contrast comprises:
computing the lightness of the input image and a lightness of the image into which the input image has been mapped in the mapping of the image data;
filtering luminance data of each of pixels constituting the input image and luminance data of each of pixels constituting the image into which the input image has been mapped;
computing a contrast ratio index and a contrast index with respect to the input image according to the filtered luminance data and average luminance data with respect to all of the pixels constituting the input image; and
increasing a local contrast of a pixel region corresponding to the parameter according to the contrast index and the contrast ratio index.
10. The method of claim 9 , wherein the parameter is data corresponding to a duration of sensed illuminance.
11. The method of claim 9 , wherein, when image data corresponding to RGB image data of an arbitrary pixel of the input image is not set in the generated LUT, the mapping of the image data comprises interpolating adjacent image data and mapping the interpolated image data.
12. The method of claim 9 , wherein:
the contrast index is determined by an equation:
contrast_index
=
Y_mean
-
Y_pixel
Y_mean
+
Y_pixel
,
where Y_mean represents an average value of luminances of all of the pixels constituting the input image and Y′_pixel represents a luminance of each of the pixels constituting the image into which the input image has been mapped.
13. The method of claim 9 , wherein:
the contrast ratio index is determined by an equation:
contrast_ratio
_index
=
Y_pixel
_fitered
Y_pixel
or
,
contrast_ratio
_index
=
Y
′
_pixel
_filtered
Y
′
_pixel
,
where Y_pixel represents a luminance of each of the pixels constituting the input image, Y_mean represents an average value of luminances of all of the pixels constituting the input image, Y_pixel_filtered represents a filtered Y_pixel, Y′_pixel represents a luminance of each of the pixels constituting the image into which the input image has been mapped, and Y′_pixel_filtered represents a filtered Y′_pixel.
14. The method of claim 9 , wherein the increasing of the local contrast comprises determining whether the corresponding pixel region is a dark region or a light region according to the contrast index.
15. The method of claim 14 , wherein, when it is determined that the corresponding pixel region is the dark region, the increasing of the local contrast further comprises decreasing a luminance of the corresponding pixel region using the parameter.
16. The method of claim 14 , wherein:
when determined that the corresponding pixel region is the light region, the increasing of the local contrast further comprises:
determining whether to increase the local contrast of the corresponding pixel region according to the contrast ratio index; and
increasing a luminance of the corresponding region using the parameter when it is determined that the local contrast of the corresponding region needs to be increased.Cited by (0)
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